test_that("simulate_traits works", {
  # given
  plink_file <-
    gsub("\\.bed",
         "",
         system.file("testdata", "test.bed", package = "smer"))
  out_file <- tempfile()
  additive_heritability <- 0.3
  gxg_heritability <- 0.1
  additive_snps <- sort(sample(1:100, 50, replace = F))
  gxg_group_1 <- sort(sample(additive_snps, 10, replace = F))
  gxg_group_2 <- sort(sample(setdiff(additive_snps, gxg_group_1), 10,
                             replace = F))
  target_mean <- 0
  target_var <- 1
  column_names <- c("FID", "IID", "TRAIT")
  n_samples <- 200
  # when
  simulate_traits(
    plink_file,
    out_file,
    additive_heritability,
    gxg_heritability,
    additive_snps,
    gxg_group_1,
    gxg_group_2
  )
  observed <- read.table(out_file, header = T)
  # then
  expect_equal(colnames(observed), column_names)
  expect_equal(nrow(observed), n_samples)
})

test_that("simulate_traits works for zero gxg heritability", {
  # given
  plink_file <-
    gsub("\\.bed",
         "",
         system.file("testdata", "test.bed", package = "smer"))
  out_file <- tempfile()
  additive_heritability <- 0.3
  gxg_heritability <- 0.0
  additive_snps <- sort(sample(1:100, 50, replace = F))
  gxg_group_1 <- sort(sample(additive_snps, 10, replace = F))
  gxg_group_2 <- sort(sample(setdiff(additive_snps, gxg_group_1), 10,
                             replace = F))
  target_mean <- 0
  target_var <- 1
  column_names <- c("FID", "IID", "TRAIT")
  n_samples <- 200
  # when
  simulate_traits(
    plink_file,
    out_file,
    additive_heritability,
    gxg_heritability,
    additive_snps,
    gxg_group_1,
    gxg_group_2
  )
  observed <- read.table(out_file, header = T)
  # then
  expect_equal(mean(observed$TRAIT), target_mean)
  expect_equal(var(observed$TRAIT), target_var, tolerance = 2e-1)
})